How to drain elixer

Before you go offline (before you are vulnerable to getting attacked) train your main army to fill your army camps. And then fill your barracks with Wall breakers. That will take up quite a few elixir of off your storage(a few hundred thousand based off of your army camp levels). But remember to "Untrain" your wall breakers before you empty your army camps (by attacking) because then you'd be stuck with an army of wall breakers which you'll just have to waste. Another advantage here is that you're not actually wasting the elixir you're just using the barracks as an alternative elixir storage that can not be farmed. Hope this helps.

You can use Elixir on troops, in particular high-Elixir cost troops relative to camp spaces. The most expensive Elixir-to-camp unit is the Wallbreaker, but obviously don't use an army of mostly Wallbreakers. Good examples of spending extra Elixir on troops are using Wizards over Archers, and all Dragon-armies (only use against air-weak camps).

At higher levels, you can also upgrade level 8 walls or above using Elixir. It's a great way to use more Elixir whilst you're still upgrading things with Gold but have finished the other Elixir upgrades.